cowper-coles



S. 0. CUWPEB-COLES, ELECTBODEPUSITION 0F ZINC UPON IRON.

(Application filed Dec. 81, 1897.)

No. 623,888. Patented Apr. 25, I899.

(No Model.)

llwrrno STATES PATENT muons SI'IERARD O. COWVPER-COLES, OF LONDON, ENGLAND.

ELECTRODEPOSITION OF ZINC UPON IRON.

SPECIFICATION forming part of Letters Patent No. 623,888, dated April 25, 1899.

Application filed December 31,1897. Serial No. 665,179. (No specimens.)

T0 ctZZ whom, it may concern:

Be it known that I, SHERARD OSBORN Cow'- 'PER-COLEs,engineer,a subject of the Queen of Great Britain and Ireland, residing at 39 Victoria street, Westminster, London, England, have invented certain Improvements in Electrodeposition of Zinc, (for which I have obtained a patent in Great Britain, No. 2,999, dated January 11, 1895,) of which the following is a specification. This invention relates to the electrodeposi tion of zinc upon iron or other metals or alloys, and has for one of its objects to provide means whereby agood, bright, and thick deposit of zinc can be obtained in an efficient manner without the formation of zinc sponge.

There is employed according to this invention in the depositing tank or cell an electrolyte or solution composed of zinc sulfate, to which is added iron sulfate, as hereinafter more particularly explained. Excellent bright deposits of zinc upon iron, for example, can be obtained by using the following proportions of the constituents to each gallon of water employed in making the solution: zinc sulfate thirty-five ounces and iron sulfate twelve ounces; but I do not limit myself to these proportions nor to using the pure saltsas, for instance, the dross formed in hot galvanizing-baths or the sick or spent solution from sulfuric-acid picklingtanks can be used, orthe sulfate of iron can be crystallized from it for use in the electrolyte. Iron sulfate as found in commerce is a ferrous salt; but I find it advantageous to partially convert itinto ferric salt, which may be done by means of atmospheric air or oxygen, or ozone, or bichromate of sodium, or any other suitable oxidizing agent. This oxidizing treatment may be applied to the iron sulfate before or after it is added to the sulfate of zinc. The solution or electrolyte is preferably used with zinc-dust or zinc in a finely-divided condition suspended in the solution or electrolyte and kept suspended therein by any suitable means or placed at the bottom of the tank or cell and stirred up at intervals; but where very smooth coatings are desired it is preferred to regenerate the solution or electolyte by passing it into a separate vessel and there dispersing through it by mechanical agitation, fire heat, or other means zinc-dust or finely-divided zinc, so as to reconvert into sulfate of zinc acid which has been formed by reason of the deposit of zinc from the solution or electrolyte in the process of electrodeposition. If the quantity of sulfate of iron in the electrolyte should fall short of the quantity required to maintain the brightness of the deposit, a further quantity of iron salt can be added to the electrolyte,'or any oXid of iron produced in the regenerating-vat can be dissolved by sulfuric acid of any desired strength and the solution so formed be added to the electrolyte. The anodes may be of any suitable materialfor instance, i rpn, lead, or carbon.

By the use of an insoluble anode oxygen is liberated from the water when the zinc is deposited, and thereby the formation of hydrogen compounds of zinc, and consequently of zinc sponge, is prevented, the reason being that the oxygen liberated at the anode converts the sulfate of iron which was added to the solution to the ferric condition, and it is reduced from the said ferric to the ferrous condition at the cathode by the hydrogen liberated.

In the accompanying drawings, Figure 1 is a diagrammatical View, and Fig. 2 is a section on line 2 of Fig. 1, of a plant or system suitable for carrying out my invention.

In said drawings, A represents a dynamo for supplying the electric current.

B B are the zincking-tanks or electrolytic cells.

D D are regenerators for the electrolyte. E is a steam-heater associated with said. regenerators.

F is a caustic-bath tank, G a picklingtank, and H a washing-tank. The cathodeplates alone are cleansed in the pickling-tank, wherein a weak solution of sulfuric acid or hydrochloric acid, or both, may be used.

I is a switchboard for the dynamo-current, and K is a donkey-engine and pump connected with the pipes leading from the regenerators to the zincking-tanks for pumping the liquid from one to the other.

I claim-- 1. The process of depositing zinc electrolytically and preventing the formation of zinc sponge, by placing in an electrolytic cell containing suitable insoluble anode and cathode plates an electrolyte containing zinc sulfate and iron sulfate, and passing through the cell an electric current, the oxygen liberated at the anode when zinc is deposited preventing the formation of hydrogen compounds of zinc or zinc sponge, as set forth.

2. The process of depositing zine electrolytically by passing an electric current through an electrolyte containing zinc sulfate and ferric sulfate, the latter being reduced to the ferrous state by the hydrogen liberated at the cathode, as set forth.

The process of depositing electrolytically by passing an electric current through an electrolyte containing zinc sulfate and sulfate of iron partly in aferrous and partly in a ferric condition, as set forth.

l. An electrolyte for use in the electrodeposition of zinc, containing zinc sulfate and iron sulfate and zinc in a finely-divided state, substantially as described.

5. The process of revivifying an electrolyte containing zinc sulfate and iron sulfate for use in the eleotrodeposition of zinc,cousisting in adding thereto zinc in a finely-divided state, substantially as described.

In testimony whereof I have signed my name to this specification in the presence of two subscribing witnesses.

S. O. C(JlVPER-COLES.

\Vitnesses:

HENRY DENIS IIosKINs, JOHN E. NFAvToN. 

